Aluminum Rubik's Cube

May 2016   Bianchini-Love

Project Documents

This is a long term project primarily for learning purposes and a novel product. I admire design and art, so this build can be considered an art project depending on the way you look at it. I'm working on this project with Bibit as my machining skills can easily use the help of an actual mechanical engineer. The goal is to create an Rubik's cubed machined out of aluminum that is the size of a standard Rubik's cube with 0.75" sub-cubes. Some adjustments are being made as the build progresses, so stay tuned for updates!

Design and conception

After spending the majority of January 2016 playing with Rubik's cubes with friends, by the time summer came around and new projects were on my mind, an aluminum Rubik's cube was something I really wanted to make.  It turns out that this has been done before, but I realized this after I was set on this project.  Something about the plastic Rubik's cubes appeal to me a lot - the solid colors, the rounded edges, and the spring-y action.  I wanted to preserve all of this while making this aluminum one.  Lu Laboratories (referenced above) was an excellent resource in gathering information pertaining to the dimensions and measurements, though some executive design decisions were made to accommodate our design and/or if we thought something would work better.

Over the summer, I modeled everything using Autodesk Inventor, choosing hardware that was readily available on McMaster-Carr.  As stated, I wanted to keep the overall look of the cube the same, but didn't want to use stickers as those tend to peel sooner than one would like.  I eventually settled on inserting a small square of 1/16" sheet aluminum into each outside face of each sub-cube of the cube.  The cool part about this is that the owner could theoretically replace these inserts (if they like unscrewing screws!) to give the cube a completely different aesthetic.  Possible ideas for inserts include anodized aluminum, powder coated aluminum (what I eventually settled on), wood, and even plastic, such as colored acrylic.

By the end of the summer, a CAD model existed of the cube, utilizing springs, screws, and materials that were feasible to obtain.

Some screenshots of the CAD

There are 6 unique parts to this design:

• 1 core piece
• 6 center face stems
• 54 colored face plates
• 6 center faces
• 12 edge pieces
• 8 corner pieces

Hardware

Fabrication

This is the challenging part. Half of fabrication is coming up with a sound way to actually produce what you want to make.  What tools are available, what time is the shop open, do I need my own tool bits and end mills?  To me it made most sense to build the cube from inside out.  That way, as you build, you could assemble the parts as you go, checking tolerances and fits, not having to wait until the end to check everything all at once.

Core Piece

Over the summer, I visited MITERS a few times to get some fabrication advice and to try a go at making the core piece of the cube.  After discussing with Michael, and assessing the the tools available, I set up on the Bridgeport using a boring head in a non-traditional way.  We flipped the boring head around such that the bit cut the outside diameter of the stock (as opposed to cutting an inside diameter).

Machining core piece #1 (top) and the outcome (bottom)

This biggest problem with this method of manufacturing was the fact that the boring head protruded a bit below the cutting tool.  Therefore, some of the sides of the cylindrical arms were flattened. I was not too excited by the results, but hey, it's something!

Come fall semester, Bibit hopped on board this project, and we continued to think about ways to make this core piece such that we could obtained better results.  Most of the machining work from here on out was performed in the Area 51 shop on Prototrak mills and lathes, with Pat McAtamney serving as an invaluable mentor and resource.  Correct machining is a must in this project, so we set out to determine speeds and speeds that produced adequate surface finishes.  These parts were milled on a Prototrak mill.

Testing speeds and feeds for the core piece

After a lot of trials, we finally arrived at something we were satisfied with.  Material is 6061 Aluminum.  Measurements are in inches.  Endmill is 1/2" diameter.  These are the settings for a circle profile:

Core piece #2 was machined in the MIT Hobby Shop, this time without using a boring head and instead using a circular profile event on a Prototrak mill. First step was to produce a cube from our 1" bar stock, drill screw holes, machine the arms, and then tap all the holes. Here is a compilation of the core piece as the arms are machined:

Core piece progression

Machining core piece #2

Core piece #2 finished with and without stems attached

Center Face Stem

The purpose of these parts are to interface the core piece with the center faces.  Initially these parts were going to be machined out of aluminum, but because aluminum tends to bind to itself when threaded together, the material of this piece was changed to steel.  These parts were machined on a Prototrak lathe.  Bibit had the brilliant idea to take a time-lapse while we produced these parts:

Time-lapse (left) and single point threading (right)

In the end, we were left with six, steel, stem pieces for our Rubik's cube:

The finished stem pieces

For reference, here are the parameters we used to turn the OD of the parts.  Material is Multipurpose O1 Tool Steel.  Measurements are in inches.  These are the settings for a turn event:

And here are the parameters used to cut the thread.  These are the settings for a thread event:

Face plates

As stated before, the face plates of the cube are small squares of 1/16" aluminum that are inset into each sub-cube.  Color is added by powder coating the squares.  Sheet aluminum was cut into 4"x4" squares that we brought to Artisan's Asylum to powder coat using their sprayer and oven.

Powder coating at Artisan's Asylum

Aluminum sheets for face plates, before (left) and after (right) firing

We've gone through several ideas while thinking about how to make these parts.  Initially, the plan was to use an Othermill to fabricate the face plates, however, after initial testing and trial runs, we soon realized we were not getting the tolerances we desired using this tool.

 We first tried cutting wood to get the hang of things, then transitioned over to Aluminum.  Here are some runs we did on the Othermill:

Cutting face plates in both wood and aluminum

The finished face plate with screws

The plan for the future is to use VHB tape to fasten the sheet aluminum to a larger piece of stock (to grip in the vise) and route the pieces on the Prototrak mill.  Stay tuned for this!

Center Faces

The center faces are the only sub-cubes that are physically attached to parts of the cube; the edges and corner pieces simply ride in the spherical volume the center faces create together.  Each center face has an adjustment hole through the middle of it.  This allows the user to adjust the tension of the tension screws without having to take apart the entire cube.  Tension adjustment requires the removal of just the center face plate.

Rendering of center face that shows tension adjust hole in the middle of the piece

With a test face plate machined, the first course of action was to determine the depth of the pocket in all the sub-cubes.  A test block was made with pockets of different depths in order to physically feel what each pocket depth was like.

Machining the pockets

Face plate pockets

Pocket depths of 0.0625", 0.0525", 0.0725", 0.0775", 0.0825", and 0.0875" were machined with a depth of 0.0725" being preferred.  Here are the settings used for milling these pockets (0.0725" depth):

With pocket depth determined, construction of the center faces began.  The sequence of machining was as follows: square stock (0.75" x 0.75" x 0.45"), drill adjustment and stem holes, cut curvatures, round corners, mill pocket, then drill and tap holes.

Corner rounding the center face

The first finished center face

As you can see in the picture to the right, the face plate screws do not line up exactly with the holes in the center face.  Because of this, the Othermill will not be used for machining the colored face plates.

Stay tuned for the machining of the rest of these pieces!

Edge Pieces

These still have yet to be machined!

Corner Pieces

These still have yet to be machined!